1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device having a thin film transistor (TFT) formed using a semiconductor film.
2. Description of the Related Art
In recent years, a TFT has been formed using a semiconductor film (a thickness of approximately several to several hundreds of nanometers) which is formed over a substrate having an insulating surface.
A silicon film can be given as an example of a semiconductor film which serves as an active layer. A silicon dangling bond exists in a silicon film, which has neither bonding between silicon atoms (Si—Si bonding) nor bonding between a silicon atom and an oxygen atom in an oxide film which is disposed close to the active layer (Si—O bonding). Since a dangling bond functions as an interface state which traps and releases electric charges, there is a concern that reliability of a TFT and a semiconductor device might be adversely affected (see Patent Document 1: Japanese Published Patent Application No. 2006-173439).
The semiconductor film is covered with an insulating film containing hydrogen and heat treatment is performed, whereby the dangling bonds in the semiconductor film are terminated (see Non-Patent Document 1: Yuichiro Mitani et at, Extended Abstracts of the 12th Workshop on Gate Stack Technology and Physics, pp. 67-72 (2007)).